The present invention relates to a noise reduction technique for a semiconductor integrated circuit and more specifically to a technique which may be effectively adapted to a semiconductor integrated circuit device comprising an analog section and a digital section for common use of signal input pin for test and signal input/output pin for usual operation, for example, to a technique which may be effectively used for LSI (Large Scale Integrated circuit) which is used in a hand-held telephone set for radio communication to process the transmitting and receiving signals.
There has been proposed a technique to reduce the number of pins through common use of the signal input/output pin for test and the signal input/output pin for normal operation in a semiconductor integrated circuit mounting a test circuit. Moreover, in recent years, an LSI comprising the analog and digital sections, in which an analog circuit and a digital circuit are mounted on the same semiconductor chip, has also been proposed in response to further improvement in packing density of LSI.
In such LSI comprising the analog and digital circuits, when it is required to use in common the signal input/output pin for testing and the signal input/output pin for normal operation, the input/output pin for testing corresponding to the test circuit of the digital section and the input/output pin for testing corresponding to the test circuit of analog section have been provided individually in order to prevent deterioration in accuracy due to noise leakage to the analog section from the test circuit of the digital section because the analog circuit requires a higher degree of accuracy. Namely, it has been avoided to use in common the input/output pin for testing corresponding to the test circuit of the digital section and the input/output pin for usual operation of the analog section.